Neutron star and black hole. Neutron stars and black holes
This post is a summary of the fifth lesson in the astrophysics course program for high school. It contains a description of supernova explosions, processes of formation of neutron stars (pulsars) and stellar-mass black holes, both single and multi-layered. star couples. And a few words about brown dwarfs.
First, I will repeat the picture showing the classification of types of stars and their evolution depending on their masses:
1. Outbursts of novae and supernovae.
The burning of helium in the depths of stars ends with the formation of red giants and their outbursts as new with education white dwarfs or the formation of red supergiants and their outbursts as supernovae with education neutron stars or black holes, as well as nebulae from the shells ejected by these stars. Often the masses of the ejected shells exceed the masses of the “mummies” of these stars - neutron stars and black holes. To understand the scale of this phenomenon, I will provide a video of the supernova 2015F explosion at a distance of 50 million light years from us. years of galaxy NGC 2442:
Another example is the supernova of 1054 in our Galaxy, as a result of which the Crab Nebula and a neutron star were formed at a distance of 6.5 thousand light years from us. years. In this case, the mass of the resulting neutron star is ~ 2 solar masses, and the mass of the ejected shell is ~ 5 solar masses. Contemporaries estimated the brightness of this supernova to be about 4-5 times greater than that of Venus. If such a supernova erupted a thousand times closer (6.5 light years), then it would sparkle in our sky 4000 times brighter than the Moon, but a hundred times fainter than the Sun.
2. Neutron stars.
Stars of large masses (classes O, B, A) after the combustion of hydrogen into helium and in the process of combustion of helium mainly into carbon, oxygen and nitrogen enter a fairly short stage red supergiant and upon completion of the helium-carbon cycle, they also shed the shell and flare up as "Supernovae". Their depths are also compressed under the influence of gravity. But the pressure of the degenerate electron gas can no longer, like in white dwarfs, stop this gravitational self-compression. Therefore, the temperature in the bowels of these stars rises and thermonuclear reactions begin to occur in them, as a result of which the following elements Periodic tables. Up to gland.
Why before iron? Because the formation of nuclei with a high atomic number does not involve the release of energy, but the absorption of it. But taking it from other nuclei is not so easy. Of course, elements with high atomic numbers are formed in the depths of these stars. But in much smaller quantities than iron.
But then evolution splits. Not too massive stars (classes A and partially IN) turn into neutron stars . In which electrons are literally imprinted into protons and most of The star's body turns into a huge neutron core. Consisting of ordinary neutrons touching and even pressed into each other. The density of the substance is on the order of several billion tons per cubic centimeter. A typical neutron star diameter- about 10-20 kilometers. Neutron star - the second stable type of "mummy" dead star. Their masses typically range from about 1.3 to 2.1 solar masses (according to observational data).
Single neutron stars are almost impossible to see optically due to their extremely low luminosity. But some of them find themselves as pulsars. What it is? Almost all stars rotate around their axis and have a fairly strong magnetic field. For example, our Sun rotates around its axis in about a month.
Now imagine that its diameter will decrease a hundred thousand times. It is clear that, thanks to the law of conservation of angular momentum, it will rotate much faster. And the magnetic field of such a star near its surface will be many orders of magnitude stronger than the solar one. Most neutron stars have a rotation period around their axis of tenths to hundredths of a second. From observations it is known that the fastest rotating pulsar makes just over 700 revolutions around its axis per second, and the slowest rotating one makes one revolution in more than 23 seconds.
Now imagine that such a star’s magnetic axis, like the Earth’s, does not coincide with the axis of rotation. Hard radiation from such a star will be concentrated in narrow cones along the magnetic axis. And if this cone “touches” the Earth with the rotation period of the star, then we will see this star as a pulsating source of radiation. Like a flashlight rotated by our hand.
Such a pulsar (neutron star) was formed after a supernova explosion in 1054, which occurred just during the visit of Cardinal Humbert to Constantinople. As a result of which there was a final break between the Catholic and Orthodox churches. This pulsar itself makes 30 revolutions per second. And the shell it ejected with a mass of ~ 5 solar masses looks like Crab Nebula:
3. Black holes (stellar masses).
Finally, fairly massive stars (classes ABOUT and partially IN) finish their life path the third type of "mummy" - black hole. Such an object arises when the mass of a stellar remnant is so large that the pressure of contacting neutrons (the pressure of a degenerate neutron gas) in the depths of this remnant cannot resist its gravitational self-compression. Observations show that the mass boundary between neutron stars and black holes lies in the vicinity of ~2.1 solar masses.
It is impossible to observe a single black hole directly. For no particle can escape from its surface (if it exists). Even a particle of light is a photon.
4. Neutron stars and black holes in binary star systems.
Single neutron stars and stellar-mass black holes are practically unobservable. But in cases where they are one of two or more stars in close star systems, such observations become possible. Because with their gravity they can “suck out” the outer shells of their neighbors, which still remain normal stars.
With this "suction" around a neutron star or black hole, a accretion disk, the matter of which partially “slides” towards a neutron star or black hole and is partially thrown away from it in two jets. This process can be recorded. An example is the binary star system in SS433, one component of which is either a neutron star or a black hole. And the second one is still an ordinary star:
5. Brown dwarfs.
Stars with masses noticeably less than the solar mass and up to ~0.08 solar masses are class M red dwarfs. They will operate on the hydrogen-helium cycle for a time greater than the age of the Universe. In objects with masses less than this limit, for a number of reasons, a stationary long-running thermonuclear fusion is not possible. Such stars are called brown dwarfs. Their surface temperature is so low that they are almost invisible in optics. But they shine in the infrared range. For the combination of these reasons, they are often called substars.
The mass range of brown dwarfs is from 0.012 to 0.08 solar masses. Objects with a mass less than 0.012 solar masses (~ 12 Jupiter masses) can only be planets. Gas giants. Due to slow gravitational self-compression, they radiate noticeably more energy than they receive from their parent stars. Thus, Jupiter, based on the sum of all ranges, emits approximately twice as much energy as it receives from the Sun.
Theoretically, any cosmic body can turn into a black hole. For example, a planet like Earth would need to shrink to a radius of a few millimeters, which is, of course, unlikely in practice. In the new issue with the “Enlightener” award, T&P publishes an excerpt from the book by physicist Emil Akhmedov “On the Birth and Death of Black Holes,” which explains how celestial bodies turn into black holes and whether they can be seen in the starry sky.
How are black holes formed?
*If some force compresses heavenly body to the Schwarzschild radius corresponding to its mass, then it will bend space-time so much that even light will not be able to leave it. This means that the body will become a black hole.
For example, for a star with the mass of the Sun, the Schwarzschild radius is approximately three kilometers. Compare this value with the actual size of the Sun - 700,000 kilometers. At the same time, for a planet with the mass of the Earth, the Schwarzschild radius is equal to several millimeters.
[…]Only gravitational force is capable of compressing a celestial body to such small sizes as its Schwarzschild radius*, since only gravitational interaction leads exclusively to attraction, and actually increases unlimitedly with increasing mass. Electromagnetic interaction between elementary particles is many orders of magnitude stronger than gravitational interaction. However, any electric charge, as a rule, turns out to be compensated by a charge of the opposite sign. Nothing can shield the gravitational charge - the mass.
A planet like the Earth does not shrink under its own weight to the appropriate Schwarzschild dimensions because its mass is not enough to overcome the electromagnetic repulsion of the nuclei, atoms and molecules of which it consists. And a star like the Sun, being a much more massive object, does not contract due to strong gas-dynamic pressure due to the high temperature in its depths.
Note that for very massive stars, with a mass greater than one hundred Suns, compression does not occur mainly due to strong light pressure. For stars more massive than two hundred Suns, neither gas-dynamic nor light pressure is sufficient to prevent the catastrophic compression (collapse) of such a star into a black hole. However, below we'll talk about the evolution of lighter stars.
The light and heat of stars are products of thermonuclear reactions. This reaction occurs because there is enough hydrogen in the interior of stars and the matter is highly compressed under the pressure of the entire mass of the star. Strong compression makes it possible to overcome the electromagnetic repulsion of identical charges of hydrogen nuclei, because a thermonuclear reaction is the fusion of hydrogen nuclei into a helium nucleus, accompanied by a large release of energy.
Sooner or later, the amount of thermonuclear fuel (hydrogen) will be greatly reduced, light pressure will weaken, and the temperature will drop. If the mass of the star is small enough, like the Sun, then it will go through the red giant phase and become a white dwarf.
If its mass is large, then the star will begin to shrink under its own weight. There will be a collapse, which we can see as a supernova explosion. This is a very complex process, consisting of many phases, and not all of its details are yet clear to scientists, but much is already clear. It is known, for example, that further fate of a star depends on its mass at the moment before collapse. The result of such compression can be either a neutron star or a black hole, or a combination of several such objects and white dwarfs.
"Black holes are the result of the collapse of the heaviest stars"
Neutron stars and white dwarfs do not collapse into black holes because they do not have enough mass to overcome the pressure of the neutron or electron gas, respectively. These pressures are due to quantum effects that come into force after very strong compression. Discussion of the latter is not directly related to the physics of black holes and is beyond the scope of this book.
However, if, for example, a neutron star is located in a binary star system, then it can attract matter from a companion star. In this case, its mass will increase and, if it exceeds a certain critical value, collapse will occur again, this time with the formation of a black hole. The critical mass is determined from the condition that the neutron gas creates insufficient pressure to keep it from further compression.
*This is an estimate. Exact value the limit is not yet known. - Approx. author.
So, black holes are the result of the collapse of the heaviest stars. IN modern idea The mass of the star's core after burning out the thermonuclear fuel must be at least two and a half solar*. No state of matter known to us is capable of creating such a pressure that would keep such a large mass from being compressed into a black hole if all the thermonuclear fuel was burned out. We will discuss the facts that experimentally confirm the mentioned limitation on the mass of a star for the formation of a black hole a little later, when we talk about how astronomers discover black holes. […]
Rice. 7. Misconception of collapse from an outside observer's point of view as a slowing eternal fall instead of the formation of a black hole horizon
In connection with our discussion, it will be instructive to use an example to recall the interconnection of various ideas and concepts in science. This story may give the reader a sense of the potential depth of the issue being discussed.
It is known that Galileo came to what is now called Newton's law of inertial systems reference, responding to criticism of the Copernican system. The criticism was that the Earth cannot revolve around the Sun because otherwise we would not be able to stay on its surface.
In response, Galileo argued that the Earth revolves around the Sun by inertia. But we cannot distinguish inertial motion from rest, just as we do not feel the inertial motion of, for example, a ship. At the same time, he did not believe in gravitational forces between planets and stars, since he did not believe in action at a distance, and he could not even know about the existence of fields. And I would not have accepted such an abstract explanation at that time.
Galileo believed that inertial motion can only occur along an ideal curve, that is, the Earth can only move in a circle or in a circle, the center of which, in turn, rotates in a circle around the Sun. That is, there may be an overlap of different inertial motions. This last type of movement can be made more complex by adding even more circles to the composition. Such rotation is called movement along epicycles. It was invented to harmonize the Ptolemaic system with the observed positions of the planets.
By the way, at the time of its creation, the Copernican system described the observed phenomena much worse than the Ptolemaic system. Since Copernicus also believed only in motion in perfect circles, it turned out that the centers of the orbits of some planets were located outside the Sun. (The latter was one of the reasons for Copernicus’ delay in publishing his works. After all, he believed in his system based on aesthetic considerations, and the presence of strange displacements of orbital centers beyond the Sun did not fit into these considerations.)
It is instructive that, in principle, Ptolemy's system could describe the observed data with any predetermined accuracy - it was only necessary to add the required number of epicycles. However, despite all the logical contradictions in the original ideas of its creators, only the Copernican system could lead to a conceptual revolution in our views on nature - to the law universal gravity, which describes both the movement of the planets and the fall of an apple on Newton’s head, and subsequently to the concept of a field.
Therefore, Galileo denied Keplerian motion of planets along ellipses. He and Kepler exchanged letters, which were written in a rather irritable tone*. This is despite their full support of the same planetary system.
So, Galileo believed that the Earth moves around the Sun by inertia. From the point of view of Newtonian mechanics, this is a clear error, since the gravitational force acts on the Earth. However, from the point of view general theory relativity, Galileo must be right: according to this theory, in a gravitational field, bodies move by inertia along at least when their own gravity can be neglected. This movement occurs along the so-called geodesic curve. In flat space it is simply a straight world line, but in the case of a planet solar system this is a geodesic world line that corresponds to an elliptical trajectory, and not necessarily a circular one. Unfortunately, Galileo could not know this.
However, from the general theory of relativity it is known that movement occurs along a geodesic only if one can neglect the curvature of space by the moving body itself (the planet) and assume that it is curved exclusively by the gravitating center (the Sun). A natural question arises: was Galileo right about the inertial motion of the Earth around the Sun? And although this is no longer the case important question, since we now know the reason why people do not fly off the Earth, perhaps it has something to do with the geometric description of gravity.
How can you “see” a black hole?
[…] Let us now move on to a discussion of how black holes are observed in the starry sky. If a black hole has consumed all the matter that surrounded it, then it can only be seen through the distortion of light rays from distant stars. That is, if there were a black hole in such a pure form not far from us, we would see approximately what is shown on the cover. But even having met similar phenomenon, one cannot be sure that this is a black hole and not just a massive, non-luminous body. It takes some work to differentiate one from the other.
However, in reality, black holes are surrounded by clouds containing elementary particles, dust, gases, meteorites, planets and even stars. Therefore, astronomers observe something like the picture shown in Fig. 9. But how do they conclude that it is a black hole and not some kind of star?
Rice. 9. The reality is much more prosaic, and we have to observe black holes surrounded by various celestial bodies, gases and dust clouds
To begin, select a certain size area in the starry sky, usually in a binary star system or in an active galactic nucleus. The spectra of radiation emanating from it determine the mass and behavior of the substance in it. Next, it is recorded that radiation emanates from the object in question, as from particles falling in a gravitational field, and not just from thermonuclear reactions occurring in the bowels of stars. The radiation, which is, in particular, the result of mutual friction of matter falling on a celestial body, contains much more energetic gamma radiation than the result of a thermonuclear reaction.
“Black holes are surrounded by clouds containing elementary particles, dust, gases, meteorites, planets and even stars.”
If the observed region is small enough, is not a pulsar, and has a large mass concentrated in it, then it is concluded that it is a black hole. First, it is theoretically predicted that after the fusion fuel burns out there is no state of matter, which could create a pressure that could prevent the collapse of such a large mass in such a small area.
Secondly, as just emphasized, the objects in question should not be pulsars. A pulsar is a neutron star that, unlike a black hole, has a surface and behaves like a large magnet, which is one of those subtler characteristics of the electromagnetic field than charge. Neutron stars, being the result of very strong compression of the original rotating stars, rotate even faster, because angular momentum must be conserved. This leads to the creation of such stars magnetic fields, changing over time. The latter play a major role in the formation of characteristic pulsating radiation.
All found on this moment Pulsars have a mass less than two and a half solar masses. Sources of characteristic energetic gamma radiation whose mass exceeds this limit are not pulsars. As can be seen, this mass limit coincides with theoretical predictions made based on the states of matter known to us.
All this, although not a direct observation, is a fairly convincing argument in favor of the fact that it is black holes that astronomers see and not anything else. Although what can be considered direct observation and what not is a big question. After all, you, the reader, do not see the book itself, but only the light scattered by it. And only the combination of tactile and visual sensations convinces you of the reality of its existence. In the same way, scientists draw a conclusion about the reality of the existence of this or that object based on the totality of the data they observe.
Gravity is the underlying subject of many of these questions. This is the defining force in space. It holds planets in their orbits, connects stars and galaxies, and determines the fate of our Universe. Created by Isaac Newton in the 17th century, the theoretical description of gravity remains accurate enough to calculate the trajectories of spacecraft on flights to Mars, Jupiter and beyond. But after 1905, when Albert Einstein showed in his special theory of relativity that instantaneous transmission of information was impossible, physicists realized that Newton's laws would no longer be adequate when the speed of gravity-induced motion approached the speed of light. However, Einstein's general theory of relativity (published in 1916) is fairly consistent in describing even those situations where gravity is extremely strong. General relativity is considered one of the two pillars of 20th century physics; the second is quantum theory, a revolution in ideas that foreshadowed our modern understanding of atoms and their nuclei. Einstein's intellectual feat was especially impressive because, unlike the pioneers of quantum theory, he had no incentive in the form of an experimental problem. Only 50 years later, astronomers discovered objects with a sufficiently strong gravitational field in which the most characteristic and striking features of the theory could appear Einstein. In the early 60s, objects with very high luminosity - quasars - were discovered. It seemed that they needed an even more efficient source of energy than nuclear fusion, thanks to which the stars shine; gravitational collapse seemed the most attractive explanation. The American theorist Thomas Gold expressed the excitement that gripped theorists at that time. In an afternoon talk at the first major conference on the new object of relativistic astrophysics, held in Dallas in 1963, he said: “Relativists with their sophisticated work are not only a brilliant ornament of culture, but they can be useful to science! Everyone is happy: relativists, who feel that their work is being recognized, that they have suddenly become experts in a field they never knew existed; astrophysicists who have expanded their field of activity... This is all very nice, let's hope it's right." Observations using new methods of radio and X-ray astronomy supported Gold's optimism. In the 1950s, the world's best optical telescopes were concentrated in the United States, especially California. This movement from Europe occurred due to both climatic and financial reasons. However, radio waves from space can travel through clouds, so in Europe and Australia new science - radio astronomy - could develop without being influenced by weather conditions. Some of the strongest sources of cosmic radio noise have been identified. One was the Crab Nebula, the expanding remnants of a supernova explosion that Eastern astronomers observed in 1054. Other sources were distant extragalactic objects that we now understand generated energy near giant black holes. These discoveries were unexpected. The physical processes responsible for the emission of radio waves, which are now fairly well understood, were not predicted. The most remarkable unexpected achievement of radio astronomy was the discovery of neutron stars in 1967 by Anthony Hewish and Jocelyn Bell. These stars are the dense remnants left behind in the center after some supernova explosions. They were discovered as pulsars: they rotate (sometimes several times per second) and emit a powerful beam of radio waves that passes through our line of sight once per rotation. The importance of neutron stars lies in their extreme physical conditions: colossal densities, strong magnetic and gravitational fields. In 1969, a very fast (30 Hz) pulsar was discovered in the center of the Crab Nebula. Careful observations showed that the frequency of the pulses gradually decreased. This was natural if the star's rotational energy is gradually converted into a wind of particles that keeps the nebula glowing in blue light. Interestingly, the pulse rate of the pulsar - 30 per second - is so high that the eye sees it as a constant source. If it had been as bright but rotated more slowly—say, 10 times per second—the small star's remarkable properties might have been discovered 70 years ago. How would the development of 20th century physics have been different if superdense matter had been discovered in the 1920s, before neutrons were discovered on Earth? Although no one knows, it is certain that the importance of astronomy for fundamental physics would have been realized much earlier. Neutron stars were discovered by accident. No one expected that they would emit such strong and clear radio pulses. If theorists had been asked in the early 1960s how best to detect neutron stars, most would have suggested looking for X-rays. Indeed, if neutron stars emit as much energy as regular stars from a much smaller area, they should be hot enough to emit X-rays. Thus, it seemed that X-ray astronomers had best opportunities discover neutron stars. X-rays from cosmic objects, however, are absorbed in the earth's atmosphere and can only be observed from space. X-ray astronomy, like radio astronomy, received impetus from military technology and experience. In this field, US scientists have taken the lead, especially the late Herbert Friedman and his colleagues at the US Naval Research Laboratory. Their first X-ray detectors, mounted on rockets, only worked for a few minutes before falling to the ground. X-ray astronomy made great progress in the 1970s, when NASA launched the first X-ray satellite, which collected information over several years. This project, and many that followed, showed that X-ray astronomy had opened an important new window into the Universe. X-rays are emitted by unusually hot gas and particularly powerful sources. Therefore, the X-ray map of the sky highlights the hottest and most powerful objects in space. Among them are neutron stars, in which a mass at least as large as the Sun is concentrated in a volume with a diameter of slightly more than 10 kilometers. The gravitational force on them is so strong that relativistic corrections reach up to 30%. It is currently assumed that some remnants of stars during collapse can exceed the density of neutron stars and turn into black holes, which distort time and space even more than neutron stars. An astronaut who ventures inside the horizon of a black hole will not be able to transmit light signals to- as if space itself is being sucked in faster than light moves through it. An outside observer will never know the final fate of the astronaut. It will seem to him that any clock falling inside will go slower and slower. So the astronaut will be, as it were, pinned to the horizon, stopped in time. Russian theorists Yakov Zeldovich and Igor Novikov, who studied how time is distorted around collapsed objects, proposed the term “frozen stars” in the early 1960s. The term "black hole" was coined in 1968 when John Wheeler described how "light and particles falling from outside...fall into the black hole, only increasing its mass and gravitational pull."Black holes that are the final evolutionary state of stars, have radii from 10 to 50 kilometers. But there is now compelling evidence that black holes with masses of millions or even billions of solar masses exist at the centers of most galaxies. Some of them manifest themselves as quasars - clots of energy that shine brighter than all the stars of the galaxies in which they are located, or as powerful sources of cosmic radio emission. Others, including the black hole at the center of our Galaxy, do not exhibit such activity, but influence the orbits of stars that come close to them. Black holes, when viewed from the outside, are standardized objects: there are no signs by which one could determine how a certain black hole formed or what objects were swallowed up by it. In 1963, New Zealander Roy Kerr discovered a solution to Einstein's equations, which described a collapsed rotating object. The "Kerr Solution" has become very important, when theorists realized that it described the space-time around any black hole. A collapsing object quickly settles into a standardized state, characterized by just two numbers measuring its mass and spin. Roger Penrose, the mathematical physicist who perhaps did most to revive the theory of relativity in the 1960s, observed: "It is somewhat ironic that for the strangest and least familiar astrophysical object - the black hole - our theoretical the picture is most complete." The discovery of black holes paved the way for testing the most remarkable consequences of Einstein's theory. The emission from such objects is mainly due to hot gas falling in a spiral into a “gravity pit”. It shows a strong Doppler effect and also has an additional redshift due to the strong gravitational field. Spectroscopic study of this radiation, especially X-rays, will allow us to probe the flow very close to the black hole and determine whether the shape of space agrees with the predictions of theory.
A black hole is a neutron star, or more precisely, a black hole is one of the varieties of neutron stars.
A black hole, like a neutron star, consists of neutrons. Moreover, this is not a neutron gas, in which neutrons are in a free state, but a very dense substance with the density of an atomic nucleus.
Black holes and neutron stars form as a result of gravitational collapse, when the gas pressure in the star cannot balance its gravitational compression. At the same time, the star contracts to a very small size and very high density, so that electrons are pressed into protons and neutrons are formed.
Note that the average lifetime of a free neutron is about 15 minutes (half-life is about 10 minutes). Therefore the neutrons in neutron stars and in black holes they can only be in a bound state, as in atomic nuclei. Therefore, a neutron star and a black hole are like an atomic nucleus of macroscopic size, in which there are no protons.
The absence of protons is one difference between a black hole and a neutron star from an atomic nucleus. The second difference is due to the fact that in ordinary atomic nuclei neutrons and protons are “glued” to each other using nuclear forces (the so-called “strong” interaction). And in neutron stars, neutrons are “glued together” by gravity.
The fact is that nuclear forces also need protons to “glue” neutrons together. There are no nuclei that consist only of neutrons. There must be at least one proton. And for gravity, no protons are needed to “glue” neutrons together.
Another difference between gravity and nuclear forces is that gravity is a long-range interaction, and nuclear forces are a short-range interaction. Therefore, atomic nuclei cannot be macroscopic in size. Starting with uranium, all elements on the periodic table have unstable nuclei that decay because positively charged protons repel each other and break apart large nuclei.
Neutron stars and black holes do not have this problem, since, firstly, gravitational forces are long-range, and, secondly, there are no positively charged protons in neutron stars and black holes.
A neutron star and a black hole under the influence of gravitational forces have the shape of a ball, or rather an ellipsoid of rotation, since all neutron stars (and black holes) rotate around their axis. And quite quickly, with rotation periods of several seconds or less.
The fact is that neutron stars and black holes are formed from ordinary stars by their strong compression under the influence of gravity. Therefore, according to the law of conservation of torque, they must rotate very quickly.
Are the surfaces of black holes and neutron stars solid? Not in the sense solid, as an aggregate state of matter, but in the sense of a clear surface of a ball, without a neutron atmosphere. Apparently, yes, black holes and neutron stars have a solid surface. The neutron atmosphere and neutron liquid are neutrons in a free state, which means they must decay.
But this does not mean that if we, for example, drop some “product” made of neutrons with the density of an atomic nucleus onto the surface of a black hole or a neutron star, then it will remain on the surface of the star. Such a hypothetical “product” will immediately be “sucked” into the interior of a neutron star and a black hole.
The difference between black holes and neutron stars
The gravity of a black hole is such that the escape velocity on its surface exceeds the speed of light. Therefore, light from the surface of a black hole cannot forever go into open space. Gravitational forces bend the light beam back.
If there is a light source on the surface of a black hole, then the photons of this light first fly upward, and then turn and fall back to the surface of the black hole. Or these photons begin to rotate around the black hole in an elliptical orbit.
The latter occurs on a black hole on the surface of which the first escape velocity is less than the speed of light. In this case, the photon can escape from the surface of the black hole, but it becomes a permanent companion of the black hole.
And on the surface of all other neutron stars that are not black holes, the second escape velocity is less than the speed of light. Therefore, if there is a light source on the surface of such a neutron hole, then photons from this light source leave the surface of such a neutron star in hyperbolic orbits.
It is clear that all these considerations apply not only to visible light, but also to any electromagnetic radiation. That is, not only visible light, but also radio waves, infrared rays, ultraviolet, x-rays and gamma radiation cannot leave a black hole. The maximum that photons of these radiations and waves can do is begin to rotate around a black hole if for a given black hole the speed of light is greater than the first cosmic speed on the surface of the star.
That is why such neutron stars are called “black holes”. Nothing flies out of a black hole, but anything can fly in. (We will not consider the evaporation of black holes due to quantum tunneling here.)
That is, it is clear that there is actually no hole in space there. Just like there is no hole in space at the location of an ordinary neutron star or at the location of an ordinary star.
If we could stand on the surface of a black hole, then looking up we would see a translucent mirror instead of a starry sky. That is, we would see there both the surrounding space (since the black hole receives all the radiation sent to it) and the light that returns to us without being able to overcome gravity. This return of light back has a mirror effect.
Exactly the same translucent “mirror” on the surface of a black hole occurs for other types of electromagnetic radiation (radio waves, X-rays, ultraviolet, etc.)
